Superfluid, Superconducting, and Magnetic Ordering in Mesoscopic Quantum Dots

A. Kadlecová, Martin Žonda, Vladislav Pokorný +1 more

Aleksandr F. Andreev

The nature of superfluid, superconducting, and magnetic ordering is elucidated for mesoscopic systems in which the single-particle level spacing is much larger than both the temperature and the critical temperature of ordering. Ordering is defined as a spontaneous violation of symmetry, the gauge invariance and time reversal being by definition symmetries violated in superfluidity (superconductivity) and magnetism contexts, respectively. Superfluidity and superconductivity are realized in thermodynamic equilibrium states with a non-integral average number of particles and are accompanied by the spontaneous violation of time homogeneity. In Fermi systems two types of superfluidity and superconductivity are possible which are characterized by the presence of pair or single-particle 'condensates'. The latter is remarkable in that spontaneous violation of fundamental symmetries such as spatial 2? rotation and double time reversal takes place. Possible experiments on metallic nanoparticles and ultracold atomic gases in magnetic traps are discussed.

英明 高柳, 淳作 新田, 勇人 中ノ

Mesoscopic Effects in Superconductors Quantum Modulation of Superconducting Junctions Superconducting Qubits Unconventional Superconductors Quantum Information Quantum Dots and Kondo Effects Quantum Wires Low-Dimensional Electrons Quantum Interference Coherence and Order in Exotic Materials.

Pertti Juhani Hakonen

Mahn‐Soo Choi, Christoph Bruder, Daniel Loss

Huading Song, Dong Pan, Runan Shang +4 more

Mesoscopic Coulomb blockade (MCB) is recognized as a phase-coherent variant of the conventional Coulomb blockade that arises in systems with open contacts. In open quantum dots, MCB is enhanced by a decrease in background conductance. This occurs because the reduction in coupling strength between the quantum dot and the outer reservoir renders the system more closed, thereby facilitating the emergence of conventional Coulomb blockade. In this work, we demonstrate that the MCB in open superconducting islands exhibits an different correlation with coupling strength compared to open quantum dots. Specifically, a decrease in background conductance may result in a weakening of the MCB. This observation indicates that the MCB in superconducting islands originates from the presence of superconducting-normal interfaces.